1. Field of the Invention
The present invention relates to cooling of a radiographic imaging apparatus.
2. Description of the Related Art
Recent advances in digital technology have popularized methods for obtaining a high-quality radiographic image by converting a radiographic image into electrical signals, subjecting the objected electrical signals to image processing, and reproducing the electrical signals as a visual image on a CRT or the like. As such a method, a radiographic-image recording/reproducing system has been proposed. In the radiographic-image recording/reproducing system, a radiographic image is temporarily stored in a fluorescent substance, and a latent image is photoelectrically read out and output as a visual image by irradiation with excitation light such as laser light. Further, with recent advances in semiconductor process technology, a system for similarly taking a radiographic image with a semiconductor sensor has been developed.
Compared with a radiographic system of the related art using a photosensitive film, the above-described systems have an extremely wide dynamic range, and can obtain a radiographic image that is rarely affected by the change in irradiation amount. Also, these systems do not need chemical treatment, and can instantaneously obtain an output image, unlike the method using a photosensitive film.
FIG. 12 is a structural view of the above-described radiographic imaging system using a semiconductor sensor. Referring to FIG. 12, an imaging apparatus 2 mounted on an imaging table 1 incorporates a radiation detection sensor 3 having a detection surface on which a plurality of photoelectric conversion elements are arranged in a two-dimensional manner.
Radiation is emitted from a radiation generation unit 4 onto a subject S. The radiation passing through the subject S is converted into a visible image by the radiation detection sensor 3 via a fluorescent substance. Electric signals output from the radiation detection sensor 3 are red out by a control unit 5, are subjected to digital image processing, and are displayed as a radiographic image of the subject S on a monitor 6.
This radiographic imaging system allows instantaneous observation of the image, unlike the above-described radiographic-image recording/reproducing system that reads out an image by post-processing. In this imaging system, the imaging apparatus is mounted on the support unit dedicated to an imaging mode for, for example, a standing position or a lying position, and is selected as desired. The imaging device is fixed in a radiation room. Further, portable imaging apparatuses have recently been developed so as to be used when imaging needs to be performed in an arbitrary position.
Since such an imaging apparatus is an electronic apparatus, it includes multiple electronic components that are essential to digitalization, but have a problem of heat generation. It is necessary to efficiently radiate heat from the electronic components. Heat radiation is important not only in improving normal operation and durability of the electronic components that generate heat, but also in preventing the characteristic of the radiation detector from being changed by a rise in internal temperature of the imaging apparatus. Further, to ensure safety of the subject, there are regulations of the temperature of the surface of a portion of medical equipment the subject touches. Hence, it is necessary to limit the rise in temperature of the exterior of the imaging apparatus.
To this end, an imaging apparatus disclosed in Japanese Patent Laid-Open No. 2000-37374 is provided with a cooling mechanism that removes heat generated in the imaging apparatus by taking in air from a suction port and causing the air to flow around the imaging apparatus by an air cooling fan. Also, Japanese Patent Laid-Open No. 2005-370 proposes a cooling mechanism that switches a heat radiation path so that heat radiation can be effectively performed in accordance with the mounting manner, for example, a standing position or a lying position.
While the above-described imaging apparatus including the cooling mechanism has been used in the field of general still imaging, there is a demand to apply the imaging apparatuses to a movie taking apparatus because the imaging apparatus is smaller and lighter than an TV image pickup system of an X-ray image intensifier (II) type having an imaging area of a similar size.
Since continuous imaging is performed in movie taking, however, the amount of generated heat becomes larger than in still image taking of the related art. Moreover, since imaging is performed in various positions, it is necessary to consider the influence of the position of the imaging apparatus on heat generation.
It has also been proposed to use an imaging apparatus, which is detachable from a table, alone as a cassette type apparatus, unlike the stationary imaging apparatuses disclosed in Japanese Patent Laid-Open Nos. 2000-37374 and 2005-370. In this case, to improve cooling performance, as described above, it is necessary to mount a new cooling mechanism in the imaging apparatus. This reduces advantages of small size and light weight of the imaging apparatus. Accordingly, there is a plan for an imaging apparatus that can take a movie while being forcibly cooled from outside with a cooling unit provided in a support unit supporting the imaging apparatus.